Variation and driving factors of nitrous oxide emissions from irrigated paddy field in the arid and semiarid region

摘要

Agricultural pollution source as Nitrous oxide (Nsub2/subO) emission from irrigated paddy field as affected by overuse of chemical fertilizer application and flooding irrigation is the primary anthropogenic source of nitrogen (N) losses in the Ningxia irrigation district. The emissions variation and driving factors of Nsub2/subO emission in the large irrigation districts needs much more investigation. A static chamber-gas chromatograph method was conducted to quantify N losses from a paddy field in Lingwu Farm during 2009–2010. Three nitrogen (N) treatments were conducted, including the conventional N application rate of 300?kg?hasup?1/sup (N300), the reducing N application rate of 240?kg?hasup?1/sup (N240) and control plot (N0). The Nsub2/subO emissions due to combined effects of the fertilizer application and flood irrigation after winter dry follow was 2.86–3.27?kg?hasup?1/sup in N300. The flood irrigation at the beginning of the rice transplanting promotes Nsub2/subO emissions due to nitrification–denitrification of a richer N source provided by the N fertilizer accumulation of soil NHsub4/subsup+/sup and NOsub3/subsup-/sup. During the rice growth stage when the paddy field was submerged, Nsub2/subO emission was very low while intermittent irrigation before tillering and the maturation stages, frequent alteration of dry and wet soil condition enhance Nsub2/subO emission. The reducing N fertilizer application improved the recovery rate in rice and resulted in a less Nsub2/subO emission from irrigated paddy field in the arid and semiarid region while keeping the rice yield.